1. Field of the Invention
The present invention relates to a retainer for balls to be used for a rolling bearing in particular a ball bearing provided with such retainer.
2. Related Art
As shown in FIG. 3, normally in a ball bearing, a plurality of balls 5 are interposed between a raceway surface 2 of an inner ring 1 and a raceway surface 4 of an outer ring 3 and these balls 5 are kept at an even spacing and circumferential by a retainer 6. Conventionally, a crown shape type retainer, provided with a plurality of pockets 7 to hold the plurality of aforesaid balls 5 at even spacing and circumferential, has often been used as the retainer 6 for such a ball bearing. For reference, in FIG. 4, W designates a thickness of the retainer 6 in the direction of the ball and H designates a height of the retainer 6 in an axial direction of a shaft to be received by this ball bearing, which are called hereinafter W direction and H direction respectively.
In this crown type retainer, the ball rolling surface 8 in the pocket 7, as shown in FIG. 5 showing a conventional manner, has a radius R.sub.R larger than the radius R.sub.B of the ball 5 and is set on the spherical surface of another sphere surface having its center on the O.sub.o which is the center of the pocket 7, accordingly between the ball rolling surface 8 and the ball 5 held in the pocket 7, there is adapted to set a predetermined gap 2.delta. normally.
By the way, in the above ball bearing, in order to increase a revolution precision, prevent a surface coarsening, diminish a friction heat, control a vibration and control a wearing, after assembling a bearing, a lubricant such as a grease is adapted to be furnished on the ball rolling surface 8 and the raceway surfaces 2, 4 of the inner and outer ring 1 and 3.
However, according to the above conventional retainer 6, the ball rolling surface 8 is settled in one spherical surface; as shown in FIG. 6, when, after the ball 5 is displaced in the W direction by .DELTA. X or in the H direction by .DELTA. Y, and a further displacement of the ball 5 is limited, the ball 5 has fallen in a state where it becomes tightly to get in touch with an edge 9a of the width W direction of the pocket 7 or and edge 9b (see FIG. 6 too) of the H direction of the pocket 7 (wedgewise), thereby, as shown in FIG. 6, the lubricant is prevented from entering the ball rolling surface 8, and there occurs a phenomenon where the lubricant G deposits outside the edges 9a, 9b.
And, when such phenomenon is generated, between the ball rolling surface 8 and the ball 5 and the ball 5 and the raceway surfaces 2, 4 of the inner, outer rings, so called a grease deficiency state is generated, which invites first not only a deterioration of revolution precision, but also an increase of surface coarsening, friction heating, vibration and wearing to decrease the bearing property as well as to reduce the life of bearing.